"He couldn't celebrate," he continued. "He couldn't forget about the lives that were lost that day. He couldn't forget about the lives of the families that were impacted on that Christmas Eve."
This inspired Manning to seek out information he thought the American public deserved to know, which would "make the world a better place," Coombs said. This included day-to-day on-the-ground reports of military action that had happened more than 72 hours prior.
He also found what appears to be video footage of a 2007 Apache helicopter strike near Baghdad that led to the death of a Reuters reporter among other civilians. Manning found portions of the transcript from the air crew, sections of which appeared in David Finkel's book "The Good Soldiers," leading Manning to believe this information had already been released, Coombs said.
"He started to see that this information should be published," his attorney said. "This is one of the more important documents of our time - lifting the fog of war and showing the true nature of 21st century asymetric warfare."
"He was a little naive in thinking that the information he selected could make a difference," he added. "But he was good intentioned."
Manning's aunt and cousin were in attendance Monday, a Department of Defense official told reporters. Roughly two dozen protesters stood outside the gates to Fort Meade, chanting slogans such as "Free Bradley Now!" In a rare statement, defense attorney Coombs thanked Manning's supporters via his website Sunday evening.
The trial may last as long as 12 weeks, during which experts say more than simply Manning may become on trial.